Over the course of a year, taking cranberry capsules did nothing to stave off urinary tract infections (UTIs) among older women living in nursing homes, a US study finds.
Women taking the capsules had just as many UTIs and infection-promoting factors in their urine as women taking inert placebo pills, researchers conclude.
“I think it reinforces what many of the other studies have said so far,” said lead author Manisha Juthani-Mehta, of the Yale School of Medicine in New Haven, Connecticut.
Previous studies on the use of cranberry products like juice and capsules produced mixed results. A systematic look at that evidence published in 2012 by the Cochrane Collaboration, an international organisation that evaluates and reviews medical research, concluded “cranberry juice cannot currently be recommended for the prevention of UTIs.”
Originally, it was thought that eating or drinking cranberry products increased the acidity of urine and prevented UTIs. There was also speculation that a compound in cranberries known as proanthocyanidin prevented bacteria from adhering to the bladder wall.
For the new study, the researchers randomly assigned 185 women over 65 years old living in 21 nursing homes near Yale to take pills every day. The participants received either two capsules containing cranberry extracts including a total of 72 milligrams of proanthocyanidin, the equivalent of a person drinking a 20-ounce bottle of cranberry juice, or they got look-alike dummy pills.
At the start of the study, about a third of the women had positive urine tests for bacteria and white blood cells, which doesn’t mean the women had UTIs but these are needed elements for an infection to occur.
The researchers had a year of data on 147 women. The other women either died, withdrew from the study or were discharged from the nursing home.
Overall, there was no difference between women who took cranberry pills or placebos in the proportion who had bacteria and white blood cells in their urine at the end of the study period. Additionally, there was no difference between the two groups in the share of women who experienced symptomatic UTIs, died, were sent to hospitals or used antibiotics.
The results were published in JAMA to coincide with their presentation at the infectious disease conference known as IDWeek, which is being held in New Orleans.
“It is time to move on from cranberries,” writes Lindsay Nicolle in an editorial accompanying the new study.
“The continuing promotion of cranberry use to prevent recurrent UTI in the popular press or online advice seems inconsistent with the reality of repeated negative studies or positive studies compromised by methodological shortcomings,” writes Nicolle, of the University of Manitoba in Winnipeg, Canada. Reuters
